After making my movie file, I tried to burn to a DVD, and when the upload was almost complete, I got the message  'There are missing or unusable files in your Movie Maker project that are preventing you movie from being saved. Please check the file preparation is enabled in options, or remove the files and try again.' How can I find which of the photos is corrupted? They were all taken with the same camera, a Nikon Coolpix, within two weeks.